Duplicate movie clip issue

ok so heres my problem. im fairly new to the duplicate movieclip function and still not 100% on how to get something to work so here it is. ok i have a line which i am turning into a gun but i want the object the duplicate at the end of it so that it can be propelled from the tip of it any help would be greatly appreciated.:thumb2:

hello? could anyone please help me this project is due soon and i cant figure this out